The present invention relates to a concrete armor or erosion prevention module for protecting coastal and hydraulic structures and shorelines. These structures, particularly structures of a multiple slender-legged shape, provide a stable interlocking assembly which resists the action of waves and water currents without exceeding the structural capacity of any single component of the assembly. In general, the structures are supported by an underlying layer of stone and are held in place by gravity and by the interlocking forces between adjacent modules.